admin: Restore requireSecureKeyguard interface.

Author: Adnan Begovic <adnan@cyngn.com>
    admin: Restore requireSecureKeyguard interface.

    Change-Id: I3c0533bafdae77df953d5bff457a4efdb94167e7

Author: Michael Bestas <mkbestas@lineageos.org>
    Fix requireSecureKeyguard javadoc

    * Fixes checkapi:
      frameworks/base/core/java/android/app/admin/DevicePolicyManager.java:10935: error:
      Added method android.app.admin.DevicePolicyManager.requireSecureKeyguard() [AddedMethod]

    Change-Id: I43ff433b1813ba54620f0f0832b8d58c6c9d1378